Abstract
One of the most important results in the theory of decomposition of universal relational schemata is the equivalence of acyclicity of the hypergraph of the schema to numerous desirable properties regarding simplicity of constraints, correctness of query evaluation algorithms, and complexity of integrity maintenance. In this paper, we show that the thrust of these results is not specific to the relational model, but rather applies in a much more general context in which schemata are just sets and views are defined by surjective functions. This is accomplished by replacing the notion of hypergraph of a schema (which is specific to the relational model) with the much more general notion of pairwise definability, which is meaningful in the context of any decomposition into a set of views.
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The research reported herein was performed while the author was visiting the Department of Mathematics of the University of Oslo, Norway. He wishes to thank in particular the members of the Computational Linguistics Group for their kind hospitality during his stay there.
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Hegner, S.J. (1991). Pairwise-definable subdirect decompositions of general database schemata. In: Thalheim, B., Demetrovics, J., Gerhardt, H.D. (eds) MFDBS 91. MFDBS 1991. Lecture Notes in Computer Science, vol 495. Springer, Berlin, Heidelberg. https://doi.org/10.1007/3-540-54009-1_18
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DOI: https://doi.org/10.1007/3-540-54009-1_18
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